initial coding for packet and its tests; includes commented-out extended functionality

common/src/main/scala/net/psforever/packet/GamePacketOpcode.scala

@@ -368,7 +368,7 @@ object GamePacketOpcode extends Enumeration {
     // 0x28
     case 0x28 => noDecoder(CreateShortcutMessage)
     case 0x29 => noDecoder(ChangeShortcutBankMessage)
-    case 0x2a => noDecoder(ObjectAttachMessage)
+    case 0x2a => game.ObjectAttachMessage.decode
     case 0x2b => noDecoder(UnknownMessage43)
     case 0x2c => noDecoder(PlanetsideAttributeMessage)
     case 0x2d => game.RequestDestroyMessage.decode

common/src/main/scala/net/psforever/packet/game/ObjectAttachMessage.scala

@@ -0,0 +1,60 @@
+// Copyright (c) 2016 PSForever.net to present
+package net.psforever.packet.game
+
+import net.psforever.packet.{GamePacketOpcode, Marshallable, PlanetSideGamePacket}
+import scodec.Codec
+import scodec.codecs._
+
+/**
+  * Change the location of an item within the game's inventory system.<br>
+  * <br>
+  * The data portion of this packet defines a player, an item, and a destination.
+  * After the packet is received by the client, the item will be guaranteed to be within the player's inventory in the codified location.
+  * The "inventory" in this case includes both the player's literal grid inventory and their available equipment slots.
+  * Where the item was before it was moved is not specified.<br>
+  * <br>
+  * This packet is a complementary packet that simulates a lazy TCP-like approach to coordinating item manipulation.
+  * In some cases, the client will (appear to) proceed with what it intended to do without waiting for the server to confirm.
+  * For example, grabbing an item from an inventory position will generate a `MoveItemMessage` that defines "the player's cursor" as a destination.
+  * The client will "attach to the player's cursor" without waiting for the `ObjectAttachMessage` from the server which echoes the destination.
+  * The change is observable.
+  * Inversely, the client is blocked from detaching the item from "the player's cursor" and putting it back into the inventory on its own.
+  * It waits until it receives an `ObjectAttachMessage` in confirmation.<br>
+  * <br>
+  *  Destination codes:<br>
+  * `80` is the first pistol slot<br>
+  * `81` is the second pistol slot<br>
+  * `82` is the first rifle slot<br>
+  * `83` is the second rifle slot<br>
+  * `86` is the first entry in the player's inventory<br>
+  * `00 FA` is a special dest/extra code that "attaches the object to the player's cursor"
+  * @param player_guid the player GUID
+  * @param item_guid the item GUID
+  * @param dest a codified location within the player's inventory see above
+  * //@param extra optional; a special kind of item manipulation; the common one is `FA`
+  */
+final case class ObjectAttachMessage(player_guid : PlanetSideGUID,
+                                     item_guid : PlanetSideGUID,
+                                     dest : Int)
+  extends PlanetSideGamePacket {
+  type Packet = ObjectAttachMessage
+  def opcode = GamePacketOpcode.ObjectAttachMessage
+  def encode = ObjectAttachMessage.encode(this)
+}
+
+object ObjectAttachMessage extends Marshallable[ObjectAttachMessage] {
+//  implicit val codec : Codec[ObjectAttachMessage] = (
+//    ("player_guid" | PlanetSideGUID.codec) ::
+//      ("item_guid" | PlanetSideGUID.codec) >>:~ { _ =>
+//        ("dest" | uint8L) >>:~ ( loc =>
+//          conditional(loc == 0, "extra" | uint8L)
+//        )
+//      }
+//    ).as[ObjectAttachMessage]
+
+  implicit val codec : Codec[ObjectAttachMessage] = (
+    ("player_guid" | PlanetSideGUID.codec) ::
+      ("item_guid" | PlanetSideGUID.codec) ::
+      ("dest" | uint8L)
+    ).as[ObjectAttachMessage]
+}